Inductively-hardened steel components containing an oil duct

ABSTRACT

INDUCTIVELY-HARDENED STEEL COMPONENTS CONTAINING AN OIL DUCT EXTENDING OBLIQUELY FROM A HARDENED SURFACE THEREOF, E.G., CRANKSHAFTS, TEND TO WEAR AT THE POINT WHERE THE OIL DUCT MEETS THE SAID HARDENED SURFACE. THE INVENTION PROVIDES MEANS WHEREBY THE WEAR IS REDUCED, COMPRISING A SUPPLEMENTARY OPENING EXTENDING FROM THE HARDENED SURFACE TO THE OIL DUCT ON THE SIDE OF THE OIL DUCT WHICH MAKES AN OBLIQUE ANGLE WITH THE HARDENED SURFACE. IN ONE EMBODIMENT OF THE INVENTION THE SUPPLEMENTARY OPENING CONSISTS OF A SLOT EXTENDING FROM THE OIL DUCT, AND IN ANOTHER EMIBODIMENT THE SUPPLEMENTARY OPENING CONSISTS OF A BORE EXTENDING TO THE SAID OIL DUCT. WHERE TWO OR MORE OIL DUCTS EXTEND FROM A COMMON POINT ON THE HARDENED SURFACE OF THE STEEL COMPONENT THE SUPPLEMENTARY OPENING MAY BE A COMPLEX SLOT HAVING PORTION EXTENDING IN THE GENERAL DIRECTION OF THE SAID OIL DUCT BRANCHES.

Nov. 23. 1971 G- SEULEN ETAL INDUCTIVELY-HARDENED STEEL COMPONENTSCONTAINING AN OIL DUCT Filed Sept. 30, 1969 4 Sheets-Sheet l inrenlorsNov. 231. 1 cs. SEULEN' ETAL INDUCTIVELY-HARDENED STEEL COMPONENTSCONTAINING AN OIL DUCT Filed Sept 30, 1969 4 Sheets-Sheet i5 Nmf- 1971G. SEULEN ETAL INDUCTIVELY-HARDENED STEEL COMPONENTS CONTAINING AN 01hDUCT Filed Sept. 50, 1969 4 Sheets-Sheet 4 Inventors Wt ,ALWEWV MW\jdbflvwwwwp 67 ,MA; w W

United States Patent Ofice 3,62l,733 Patented Nov. 23, 1971 3,621,733INDUCTIVELY-HARDENED STEEL COMPONENTS CONTAINING AN OIL DUCT GerhardSeulen, Remscheid, and Hermann Kuhlbars, Remscheid-Luttringhausen,Germany, assignors to AEG-Elothern G.m.b.H., Remscheid-Hasten, GermanyFiled Sept. 30, 1969, Ser. No. 862,394 Claims priority, applicationGermany, Oct. 9, 1968, P 18 02 027.4 Int. Cl. F16c 3/14 US. Cl. 74-605 6Claims ABSTRACT OF THE DISCLOSURE Inductively-hardened steel componentscontaining an oil duct extending obliquely from a hardened surface 7thereof, e.g., crankshafts, tend to wear at the point where the oil ductmeets the said hardened surface. The invention provides means wherebythe wear is reduced, comprising a supplementary opening extending fromthe hardened surface to the oil duct on the side of the oil duct whichmakes an oblique angle with the hardened surface. In one embodiment ofthe invention the supplementary opening consists of a slot extendingfrom the oil duct, and in another embodiment the supplementary openingconsists of a bore extending to the said oil duct. Where two or more oilducts extend from a common point on the hardened surface of the steelcomponent the supplementary opening may be a complex slot havingportions extending in the general direction of the said oil ductbranches.

This invention relates to the improvement of the torsional and bendingstrengths of mechanical components, such as for example shafts,particularly crankshafts for spark-ignition and compression-ignitioninternal combustion engines, and compressors, pumps and the like.

For reasons of cost such components are usually made from unalloyed orlow alloy structural steels. For improving their wear resistance as wellas their torsional and bending strengths, it is known and is generalpractice inductively to harden the bearing surfaces and possibly thefillets at the ends of these surfaces of crankshafts and likecomponents. This treatment improves the reverse bending and torsionalstrength of the shaft to such an extent that it is capable oftransmitting 80 to 100% more power without risk of fatigue fracture.

However, the areas in such hardened components surrounding the openingsof oil ducts are critical, because in these zones, particularly at theedges of the openings, the penetration of inductive hardening is greaterthan elsewhere. This increase in the depth of the hardened zone is dueto the fact that the oil ducts impede the free flow of heat duringhardening. Moreover, in inductive hardening the current filaments aremore densely spaced around the edges of the oil ducts and thus generatea particularly large amount of heat in this region. When such componentsare inductively hardened it is therefore practically impossible to avoidthe consequence that not only the depth of the hardened zone will begreater around the oil ducts but that the oil duct edges will also beundesirably overheated, causing the hardened structure to coarsen andbecome embrittled.

When the oil ducts are straight, i.e., when the oil ducts areperpendicular to the longitudinal axis of the workpiece, there is nosignificant impairment of the inductively hardened workpiece. However ifthe oil ducts are at an acute angle to the longitudinal axis of theworkpiece the deterioration is greater as illustrated in FIG. 1 of theaccompanying drawings, which is a longitudinal section of a crankpincontaining an oil-hole. The crankpin 1 is traversed by an oil duct 2which extends directly from the pin through the web to the surface of anadjoining crankpin. The hardened zone '3 in those parts of the surfacethat contain no oil-hole is parallel to the surface. There is also noincrease in the depth of penetration in those regions of the side of theoil duct which make a right angle or as at 4', an obtuse angle with thelongitudinal workpiece axis. However where the wall of the oil ductmakes an acute angle with the longitudinal workpiece axis, as at 4", theincrease in the depth of penetration in this zone where there is aminimum accumulation of material may assume dangerous proportions, i.e.,the material may be sufficiently overheated for hardening cracks toappear when the workpiece is quenched.

After being in use for some length of time, portions of material aroundthe lip of the oil hole tend to break away. Moreover after prolonged usehair cracks appear concentrated in the region of the acute angle at 4and these likewise cause surface portions or parts of the acuteanglededge to break off. There is a considerable danger that such a break-awayof material may cause the bearings to seize by running hot and of theshaft eventually being completely destroyed. Moreover the cracks may bethe starting points of fatigue fractures.

In order to avoid the deterioration arising from the presence of the oilducts it has previously been proposed to insert metal plugs into theholes and thereby to eliminate the causes of overheating. However thismethod has not been much used because of the additional expense itinvolves.

According to another proposal the oil ducts are filled with substancesthat at a given temperature release water of crystallisation. Althoughthis also leads to a reduction of excessive temperatures the effectthereby obtained is not sufiicient.

It is an object of the present invention to provide a solution to theabove-described problem with hardened mechanical parts made of steel,such as for example crankshafts, axle shafts or the like, which partsfor the purpose of lubrication during service are provided with oilducts, particularly oil ducts set at an angle, and has for its object toimprove the wear resistance, as well as the torsional and flexuralstrength of such a part.

This improvement in resistance and strength is achieved according to theinvention by providing in the region where the accumulation of materialat the lip of the oil hole is a minimum, i.e., where the wall of the oilduct makes an acute angle with the adjoining workpiece surface, asupplementary opening between the hardened surface and the oil duct thecross-section of which is rounded at least on the side remote from thesaid oil duct. In one embodiment of the invention the said supplementaryopening has the form of a slot extending from the wall of the oil holeand which is provided with fillets at the transistions between the baseand the sides of the slot.

In another embodiment of the invention the said supplementary opening isa bore which extends from the hardened surface into the oil hole.

The width of the slot or the diameter of the bore constituting thesupplementary opening of the invention will depend upon the size of theworkpiece itself. For a conventional crankshaft of the type used in amotor vehicle, the width may for example be between 0.5 and 1.5 mm. Itdoes not matter whether this supplementary opening is provided before orafter inductive heating, as steel parts that have already been hardenedcan readily be machined by spark erosion or electrolytic techniques.

Embodiments of the invention are hereinafter described and illustratedin FIGS. 2 to 5 of the accompanying drawings, in which:

FIG. 2 and FIG. 3 are a plan view and longitudinal section respectivelyshowing features of the invention;

FIG. 4 and FIG. 4a are a plan view and a longitudinal sectionrespectively of a further embodiment of the invention, and

FIG. shows a configuration of the slot according to the invention whenseveral oil duct branches share a common entry hole in a crankshaft.

Referring to FIGS. 2 to 5 of the drawings, the plan view of thecrankshaft of FIG. 2 has an oil duct 2 which extends in the direction ofthe workpiece axis from the surface of the left-hand bearing, traversesthe web of the crank and ends in the surface of the underside of theright hand bearing. The course taken by this oil duct through the shaftis more clearly shown in FIG. 3. In the region of the acute angle 4" theoil ducts are provided with a slot 5 which has fillets 6 at its base.

A similar improvement of the properties of the crankshaft may beachieved if the slot is simply replaced by a bore 7 as in FIG. 4 andFIG. 4a. In this embodiment the occurrence of hardening cracks may notbe avoided but it has been found from experience that all these craoksextend into the bore 7 and that they do not continue beyond the bore.

The invention may also be applied when the courses taken by the oilducts are more complex, as indicated in FIG. 5 where two oil ducts 9 and10 extending at different angles share a common entry hole 2.Consequently in FIG. 5 two slots extending in the directions of thedifferent oil ducts are provided instead of only one and the two ductscombine to form a slot 8.

What is claimed is:

1. An inductively-hardened steel component containing an oil ductextending obliquely from a hardened surface thereof, in which asupplementary opening is provided in the region of the said oil ductwhere the wall of the said oil duct makes an acute angle with the saidhardened surface and where the minimum material is between said oil ductand said surface, the said supplementary opening extending from the saidhardened surface to the said oil duct.

2. An inductively-hardened steel component according to claim 1, whereinthe said supplementary opening is a slot extending from the wall of thesaid oil duct and 4 having a rounded surface at least on the side remotefrom the said oil duct.

3. An inductively-hardened steel component according to claim 1, whereinthe said supplementary opening is a bore extending from the saidhardened surface to the said oil duct.

4. An inductively-hardened steel component containing a plurality of oilduct branches extending at an angle one to the other from a common pointon the hardened surface thereof, in which a complex slot is provided inthe region of the said oil ducts where the wall of the said oil ductsmake an acute angle with the said hardened surface, the said slotextending from the said common point having slot portions extending inthe direction of the said oil duct branches, and having rounded surfacesat least on the sides remote from the said common part.

5. An inductively-hardened steel crankshaft comprising at least one oilduct extending obliquely from a hardened surface thereof, and asupplementary opening extending from the said hardened surface to thesaid oil duct at a point where the said oil duct makes an acute anglewith the said hardened surface, the cross-section of the saidsupplementary opening being rounded at least at a position remote fromthe said oil duct.

6. A component as in claim 1 wherein the width of said supplementaryopening is smaller than the diameter of said duct.

References Cited UNITED STATES PATENTS 1,293,382 2/1919 Easton 74-6051,506,513 8/1924 Wills 1846 N 2,419,408 4/ 1947 Lightowler 74-6052,489,527 I l/1949 Frank 184-6 N 2,723,003 11/1955 Antonsen 184--6 N2,800,809 7/1957 Pike 29149.5 X 3,313,016 4/1967 Seulen et al. 2.9149.53,495,685 '2/1970 Van Rinsum 184-6 N WILLIAM F. OD'EA, Primary ExaminerF. D. SHOEMAKER, Assistant Examiner US. Cl. X.R. 296, 149.5

